Hello,
Welcome to ehealthforum and thanks for writing
The symptoms described by you can be due to various possibilities as muscle strain, intraabdominal pathology such as tender and enlarged spleen, colon problems, pancreatitis etc. Stress and anxiety could also cause similar symptoms.Since you do not have any other symptoms as fever,indigestion,vomitting,loose stools the likely cause is muscular strain or Anxiety associated symptoms.
You may try anti inflammatory medications such as Ibuprofen 200mg twice a day after food for few days. Warm compression using hot water bags on the affected region will also benefit you. A physical examination and tests which include sonograpy is entailed if the symptom worsen or persists for more than 2 week.Kindly consider visiting a Physician in this case.
Take care!